A conjugated diene-based polymer or a hydrogenated conjugated diene-based polymer has been heretofore used as a modifier that improves impact resistance, low-temperature properties, processability and the like of a thermoplastic resin, because of being excellent in rebound resilience and low-temperature properties, and a composition including such a polymer has been heretofore widely used in the fields of electrical/electronic components, automobile components, various industrial components, daily commodities and the like. Polymer substances different from each other in structure, however, are not generally good in compatibility and are insufficient in affinity, and therefore are sometimes poorly dispersed in each other, resulting in deteriorations in mechanical properties of a composition, and poor appearance.
There has been heretofore proposed a method of providing a composition having excellent characteristics by an enhancement in affinity of polymer substances different from each other in structure. For example, a method is reported in which a polymer reaction of two polymer substances essentially incompatible produces a graft copolymer and the copolymer is interposed to increase the adhesion strength at the interface between different polymer substances, thereby allowing excellent characteristics in practical use to be exhibited. Specifically, there is disclosed the following: a terminal functional group of a conjugated diene-based polymer or a hydrogenated conjugated diene-based polymer and a polar group of a thermoplastic resin react with each other to form a graft copolymer, thereby providing a composition having excellent mechanical properties and adhesiveness (Patent Literatures 1, 2 and 3).
In particular, a hydrogenated conjugated diene-based polymer having a nitrogen-containing functional group at an end thereof is excellent in not only rebound resilience, low-temperature properties and compatibility, but also heat resistance and weather resistance, and therefore is widely used as a modifier of a thermoplastic resin and a rubber polymer, in particular, a polymer substance such as an engineering resin having high heat deformation resistance.
A composition including such a hydrogenated conjugated diene-based polymer having an end modified is compounded with, in addition to various stabilizers and reinforcing agents, a pigment, a dye, a colorant or the like to be thereby colored, and thereafter is subjected to a step of extrusion molding, injection molding or the like to be thereby formed into a final molded product.